Researchers will study effects of exercise on abdominal aortic aneurysms

Researchers at the School of Medicine have launched a study to find non-surgical treatments for abdominal aortic aneurysms, a potentially life-threatening disease that currently is only treatable with surgery.

By studying the effects of long-term exercise on abdominal aneurysms, researchers hope to determine the exact mechanisms of how exercise can help prevent the growth of the aneurysms, and to identify potential drug therapies that mimic those mechanisms.

"There are currently no proven therapies for small aneurysms, and they never go away on their own," said Ronald Dalman, MD, professor of vascular surgery and lead investigator for the study.

Researchers are recruiting a total of 1,400 patients with small abdominal aortic aneurysms for the five-year, $17 million study funded by the National Heart, Lung and Blood Institute.

The majority of volunteers will come in for one day of testing for the first part of the study to assess lifetime physical activity, overall health history, aortic size and profile of serum markers of abdominal aortic aneurysms. About 340 of these subjects will also complete a three-year program of supervised exercise training to determine the effect of increased activity on aneurysm progression.

AAA is a weakness in the wall of the aorta and exists in 4 to 8 percent of men and 1 to 3 percent of women over age 50. The aorta, the largest artery in the body, carries blood from the heart through the chest to the abdomen where it becomes the abdominal aorta. An aneurysm forms when a weak area of the abdominal aorta expands or bulges, much like a balloon. If the aneurysm bursts, it can cause severe internal bleeding and death.

AAA rupture is one of the leading causes of death in the United States, with an estimated 15,000 people dying from AAA rupture each year.

Previous studies have shown that exercise modifies the growth of abdominal aortic aneurysms, but no one knows exactly how or why, Dalman said.

"The cardiovascular health benefits of exercise are extremely well characterized," he said. "Patients who cannot exercise regularly are at increased risk for heart disease and aneurysm disease. Patients with spinal cord injuries, who often cannot exercise their legs at all, are at even greater risk."

By studying the effects of exercise on the aneurysms, researchers hope to reduce the need for surgery. There have been recent successes in the surgical treatment of large AAAs, but when someone is diagnosed with a small aneurysm, the prescription is quite simply to "watch and wait" and see what happens. Usually that means watching the aneurysm get bigger with annual or semi-annual ultrasound exams while waiting for eventual surgery.

Many people with AAA also don't even know they have the disease because there are few symptoms. Among the apparent risk factors for the disease are being over the age of 60, smoking, atherosclerosis, high blood pressure and lack of exercise. Men also appear to be at higher risk than women.

Until recently, there were no routine tests for the disease. AAAs were most commonly found when physicians were performing an imaging test, such as an ultrasound, for another condition.

Federal legislation enacted in January now provides free minimally invasive screening for AAA in men who have smoked at any time in their lives, and for both men and women with a family history of the aneurysms. Starting in 2007, new Medicare beneficiaries at risk for AAA can receive a free ultrasound screening for the disease starting with their 65th birthday and their "welcome to Medicare" physical examination.

"The timing of our project is opportune," Dalman said. "There are going to be even more patients with small aneurysms, wandering around thinking, 'I have an aneurysm. Now what?'"

Researchers are recruiting men and women between the ages of 50 and 85 with small AAAs (less than 5 cm in size). Stanford is collaborating with Kaiser-Santa Clara and the Veterans Affairs Palo Alto Health Care System.

For more information, visit the study's Web site at: http://aaastop.stanford.edu or call Julie White at 498-6039.